1. Field of the Invention
This invention relates to a method of supplying an excited oxygen to be used in the steps of manufacturing a semiconductor device such as a very large scale integrated (VLSI) device, for example in the step of forming a thin film, etching a substrate, removing a resist, cleaning a chamber, or improving the characteristics of a thin film.
2. Description of the Related Art
An excited oxygen is useful in the steps of manufacturing a semiconductor device such as a very large scale integrated (VLSI) device, for example in the step of forming a thin film, etching a substrate, removing a resist, cleaning a chamber, or improving the characteristics of a thin film.
Out of these utilities of the excited oxygen, one example of the conventional technique of forming a silicon oxide film by means of a remote plasma CVD, which is one of the methods of forming a thin film, will be explained below.
Since the latest VLSI device is provided with a groove of high aspect ratio (depth/width), it is increasingly demanded to deposit an insulating film having an excellent step coverage in such a groove at a low temperature. As one of the methods meeting such a demand, there is known a method which makes use of the reaction between TEOS (tetraethoxysilane) and ozone. However, since the reactivity of ozone is insufficient, the film deposited by this method is poor in insulation properties, thus badly affecting the life of a VLSI device to be finally obtained. Meanwhile, a method of forming a film excellent in density and insulation properties at a low temperature by making use of a reaction between a highly reactive excited oxygen and TEOS (for example, Matsui et al, Annual Spring Meeting of Appl. Phys. Inst., 28a-SZG-8(1992)) has been proposed.
FIG. 1 illustrates a schematic view of one example of the conventional film-forming device to be employed. According to this film-forming device, an excited oxygen (mainly in the form of oxygen atom) generated at a plasma discharge zone 100 and a reaction gas of TEOS supplied from a reaction gas-supplying pipe 101 are mixed in a reaction chamber 102 located away from the plasma discharge zone 100 and reacted at a reaction zone 103, thereby forming at a low temperature (about 250 to 350.degree. C.) an oxide film on a substrate 105 heated with a heater 104. A residual gas is discharged through an exhauster 109.
An excited oxygen to be generated by plasma (such as an oxygen atom, an oxygen atom in an excited state, an oxygen molecule in an excited state) is highly reactive, so that it is effective in forming a film at a low temperature, but is short in life so that it is very difficult to produce a large quantity of the excited oxygen by means of ordinary plasma exciting method, or to transport a large quantity of the excited oxygen from a generation zone to a reaction zone. It is possible to increase the generation of excited oxygen by increasing the power of plasma. However, it will give rise to problems of the change of discharge-mode to another, or of instability of the discharge. Therefore, any attempt to increase the amount of excited oxygen by increasing the power of plasma is naturally limited.
As explained above, since the density of excited oxygen to be attained by the conventional oxygen-exciting method is low, the application of this conventional oxygen-exciting method to the formation of a film through a CVD method is inevitably resulted in a low film-growth rate. The same thing can be said if the conventional oxygen-exciting method is applied to the method of etching a substrate, removing a resist, cleaning a chamber, or improving the characteristics of a thin film. Namely, since it is impossible according to the conventional oxygen-exciting method to increase the density of excited oxygen, it can not be expected to improve the processing rate of these treatments.
As explained above, the conventional method of generating and supplying excited oxygen is accompanied with problems that it is difficult to produce a large quantity of excited oxygen and to transport a large quantity of excited oxygen from a generation zone to a reaction zone, and that only a low reaction rate would be obtainable, if the conventional method is applied to the method of forming a film, etching, removing a resist, cleaning a chamber, or improving the characteristics of a thin film.